Numerical study of microramp control of supersonic shock wave/boundary layer interaction

Periodic boundary conditions have the role of simulating the presence of a row of ramps located 3.66”TE apart from each other. This configuration allows us to significantly reduce the computational cost of the simulations, as the number of cells triples using the three ramps arrangement. However, these two setups have been compared to ensure that periodic boundary conditions do not affect the solution. The comparison was made using the Reynolds stress model as turbulence model, and the results are illustrated in Figure 3.8, where one can observe that the trends of Cf , Pw and x-wall shear stress distribution downstream of the ramps are substantially identical between the two cases, except for the zone immediately downstream of the ramp, where the shear stress relative to the three ramps configurations drops sooner and then reconcile with the one relative to the periodic BC.

These little differences can be also seen in Figure 3.9, where the darker area, i.e., the area with higher shear stress, appears longer in the single ramp case, consistently with the previous plot. Nevertheless, this behavior seems to not significantly affect the topology of the separation. Furthermore, one must consider the great computational savings relative to the use of periodic boundary conditions, which allowed us to run a single simulation in a few hours (4/5) against the 36 hours needed for the three ramps.

Thanks to these considerations, it has been possible to run the simulations with the periodic boundary conditions being sure that they represent correctly, unless minor inaccuracies, the presence of the microramps row. All the results discussed in the following sections have been obtained with this periodic configuration.